Antivenoms for Snakebite Envenoming: What Is in the Research Pipeline?

Of the 24 neglected tropical diseases (NTDs) and conditions listed by WHO, snakebite is among the top killers [1]. Tens of thousands of people die each year as a result of snakebite envenoming, with close to 50,000 deaths in India alone [2] and up to 32,000 in sub-Saharan Africa [3]. Yet there are few sources of effective, safe, and affordable antivenoms. The regions that bear the highest snakebite burden are especially underserved [4]. The Fav-Afrique antivenom, produced by Sanofi Pasteur (France), is considered safe and effective and is one of the few antivenoms to be approved by a Stringent Regulatory Authority (French National Regulatory Authority), although limited formal evidence has been published [5,6]. It is polyvalent, targeting most of the medically important snake species in sub-Saharan Africa. In particular, it is highly effective in treating envenoming by Echis ocellatus, the West African saw-scaled viper [5–7] that causes great morbidity and mortality throughout the West and Central African savannah. The venom of E. ocellatus may induce systemic haemorrhage, coagulopathy, and shock, as well as extensive local tissue damage. In the absence of treatment, the case fatality rate is 10%–20% [8]. Medecins Sans Frontieres (MSF) uses Fav-Afrique in its projects in sub-Saharan Africa, notably in Paoua in Central African Republic (CAR), where E. ocellatus envenoming is frequent [9]. Worryingly, MSF has been informed that the production of Fav-Afrique by Sanofi Aventis will be permanently discontinued. The last batch was released in January 2014, with an expiry date of June 2016. All the vials produced have already been sold by Sanofi Pasteur. Although several alternative antivenom products target a similar list of species as Fav-Afrique, there is currently no evidence of their safety and effectiveness. We aimed to review the evidence for the efficacy and safety of existing and in-development snake antivenoms, and to list the alternatives to Fav-Afrique in sub-Saharan Africa.